The invention relates to a thermoelectric fill level measuring device having sensing resistors in a container with fill material and a free space.
Level measuring devices are required to monitor and control technical processes and are widely known. The serviceability of motor vehicles depends on sufficiently accurate display of the fuel supply state. Thermoelectric fill level measurement is an improvement on potentiometric level measurement because no moving parts are required and therefore it is possible to reduce the cost of manufacture and also provide high reliability. In contrast to dielectric fill level measurement, thermoelectric level measurement is virtually independent of any poor conductivity of the filling substance, as may occur in the case of ethanol, and is also virtually independent of any fluctuations in the composition of the fuel or filling material. A serious problem in thermoelectric level measurement is that of ensuring sufficient stability and accuracy.
Therefore it was proposed in German Auslegeschrift No. 2841889 to provide a second sensing resistor which was not heated and to evaluate the difference in the resistors. This solution does in fact provide for relatively accurate detection of the fill level when the container is full but there is inaccuracy of measurement as the level falls. However, in most applications it is desired to provide accurate display of the quantity remaining, as is the case for example with motor vehicles, since incorrect display of the fuel level may result in disastrous miscalculation of the distance which can be covered with the remaining fuel.